Hi, we are currently fostering a beautiful black greyhound. Our BC/Koolie cross has taken an intense dislike to the new arrival. He is fine with him on walks and when there is a gate between them (just ignores the grey except for the occasional sniff) but if we take the grey into the back yard our dog will mouth snap at him. We're not sure how serious he is as he doesn't make contact but he also isn't backing down. We've had the grey about 3 weeks and there has been no discernible softening from our BC. He is normally fine with other dogs although our other short term fosters have all been little dogs. Would welcome any thoughts on this situation. More than anything else we are just puzzled!